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Fast and efficient synthesis of ZSM-5 under high pressure
Catalysis Communications 3 (2002) 113–117 www.elsevier.com/locate/catcom
Fast and efficient synthesis of ZSM-5 under high pressure q S.J. Kulkarni *, P. Srinivasu, N. Narender, K.V. Raghavan Catalysis and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500 007, India Received 5 September 2001; received in revised form 16 January 2002; accepted 16 January 2002
Abstract Highly crystalline ZSM-5 catalysts were synthesized in 4–6 h of autoclavation time using various solvents under high pressures ð 40–60 atmÞ and temperatures (230–250 °C) Ó 2002 Published by Elsevier Science B.V.
1. Introduction The US patent of synthesis of ZSM-5 by Argauer and Landolt [1] is the milestone in zeolite catalysis. Initially ZSM-5 was synthesized with 7 days of autoclavation time at 120–180 °C under autogenous pressure. Using nucleated gel [2,3] i.e. seeding method, the autoclavation time was further reduced to two days and the process is commercialized. The autoclavation time was further reduced to 4–12 h by the modified synthesis [4,5]. In case of promoter induced synthesis, there are various problems before it can be commercialized like phase or anion impurity, percent crystallinity, the incorporation of metal ion (e.g. As, P) in the framework tetrahedral position, the yield of the product and control of Si/Al ratio in the product. In this paper we report the synthesis of highly crystalline ZSM-5 at reduced autoclavation time,
4–10 h under high pressure and temperature without using any promoter.
2. Experimental 2.1. The seeding gel for ZSM-5 was synthesized by the following procedure The seeding gel was prepared as follows: 0.69 g (0.01725 mol) of sodium hydroxide was dissolved in 71.028 ml (3.946 mol) of distilled water. 27.7 ml (0.02875 mol) tetrapropylammonium hydroxide was added drop-wise to NaOH solution with stirring. The mixture was stirred for 30 min. Then 27.5 ml (0.1322 mol) of tetraethoxysilane was added drop-wise. The total mixture was stirred at 100 °C for about 16 h. This is used as seeding gel. 2.2. The ZSM-5 was synthesized as follows
q
IICT Communication No. 4790. Corresponding author. Tel.: +91-40-7173874; fax: +91-407173387/757. E-mail address: [email protected] (S.J. Kulkarni). *
Sodium hydroxide 0.88 g (0.22 mol) was dissolved in 25 ml of distilled water. Sodium aluminate 1.05 g (0.0128 mol) and 196 ml (4.841 mol) of methanol as a solvent were added and the mixture
1566-7367/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII: S 1 5 6 6 - 7 3 6 7 ( 0 2 ) 0 0 0 5 1 - 1
95.0 83.0 92.0 74.0 71.0 53.0 – 83.0 361 351 387 364 346 343 333 379 11.6 11.6 11.8 11.3 11.4 11.6 11.2 11.6 Acetone Isopropanol Ethanol Acetonitrile Water 2 3 4 5 6
R ¼ ðSiO2 Þ29:4 : ðAl2 O3 Þ1 : ðTempÞ0:5 : ðH2 OÞ260 .
Methanol 1
R: R: R: R: R:
ðCH3 COCH3 Þ417 ððCH3 Þ2 CHOHÞ400 ðCH3 CH2 OHÞ525 ðCH3 CNÞ586 ðH2 OÞ1701
242 242 242 230 230 233 265 260 R: ðCH3 OHÞ756
Autogenous pressure (atm) Autoclavation temperature (°C) Gel composition Solvent Entry
Fig. 1. X-ray diffraction patterns of (a) ZSM-5 (4 h, methanol), (b) ZSM-5 (6 h, methanol), (c) ZSM-5 (10 h, acetone), (d) ZSM5 (10 h, acetonitrile) (e) ZSM-5 (10 h, ethanol), (f) ZSM-5 (10 h, isopropanol).
Table 1 Synthesis of ZSM-5 with various solvents and under high pressure conditions
Time (h)
Initial pH
The experimental conditions of the synthesis of ZSM-5 are given in Table 1. We have varied the solvents in the synthesis like methanol, ethanol, acetone, acetonitrile, isopropanol and water. The
10.2 10.2 10.1 10.2 10.3 10.3 10.0 10.4
Final pH
3. Results and discussion
4 6 10 10 10 10 10 10
Surface area ðm2 g1 Þ
% Crystallinity
(Si/Al) atomic zeolite
was stirred for 30 min. Tetraethoxysilane 41.9 ml (0.1882 mol) was added drop-wise and stirred for an hour. Finally 15 g of the seeding gel was added and the mixture was stirred for 1 h. The pH of the mixture was 10.2–11.0. The total mixture was put into 600 ml Parr autoclave and stirred at 230–250 °C for 4–10 h. The solid product obtained was filtered, washed with distilled water and dried at 100–110 °C for 6 h.
27.25 – – 17.10 17.63 17.63 16.43 13.85
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
50 49 50 47 48 50 50 47
114
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
115
Fig. 2. Infra-red spectra of (a) ZSM-5 (10 h, methanol), (b) ZSM-5 (10 h, acetone), (c) ZSM-5 (10 h, ethanol), (d) ZSM-5 (10 h, isopropanol).
Fig. 3. 27 Al Solid state MAS-NMR of (a) ZSM-5 (10 h, methanol), (b) ZSM-5 (10 h, isopropanol), (c) ZSM-5 (10 h, acetone), (d) ZSM-5 (10 h, water), (e) ZSM-5 (10 h, ethanol) (f) ZSM-5 (10 h, acetonitrile).
autoclavation pressure was kept near or above critical pressure by increasing the autoclavation temperature above the critical temperature of the
solvent. The autoclavation temperature varied from 230 to 260 °C and the corresponding autogenous pressure from 45 to 50 atm. The initial pH
Table 2 Synthesis of ZSM-5a : effect of temperature Entry
Autoclavation temperature (°C)
Autogenous pressure (atm)
Gel composition
1 2 3 4
242 200 180 150
50 39 34 27
R: R: R: R:
ðCH3 OHÞ756 ðCH3 OHÞ756 ðCH3 OHÞ756 ðCH3 OHÞ756
R ¼ ðSiO2 Þ29:4 : ðAl2 O3 Þ1 : ðTempÞ0:5 : ðH2 OÞ260 . a Methanol used as a solvent.
Time (h)
Initial pH
Final pH
Surface area ðm2 g1 Þ
% Crystallinity
4 4 4 4
10.2 10.1 9.9 9.8
11.6 11.2 11.0 11.1
361 358 342 347
95.0 94.0 95.0 61.0
116
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
was 10–10.4 of gel and the final pH was 11.2–11.8. In the initial pH range of 9–10.5, the homogeneous highly crystalline product is expected with homogeneous aluminum distribution throughout the crystallite [6]. The X-ray diffraction patterns are given in Fig. 1. The XRD patterns were obtained using SIE) radiaMENS D5000, with Cu Ka (k ¼ 1:54 A tion in the range of 0–40 values of 2h. In case of methanol as a solvent the autoclavation time was varied from 4, 6 and 10 h. All the corresponding XRD patterns show high crystallinity. The XRD pattern corresponding to acetonitrile as a solvent was not good and the solid product obtained after 10 h was nearly amorphous. The percent crystallinities are given in Tables 1 and 2. The ZSM-5 catalysts which were synthesized using methanol as a solvent showed P 95% crystallinity. In case of ethanol, acetone or isopropanol as a solvent, the solid products (ZSM-5) obtained were highly crystalline with the impurity of quartz. The attempts are in progress to reduce the impurity by varying the autoclavation temperature. The IR spectra were taken using NICOLET 740 model-FTIR spectrometer, KBr pellets and given in Fig. 2. The IR spectra are characteristic of typical ZSM-5 catalyst. The (Si/Al) atomic ratio was 17 for crystalline catalysts. The surface area are given in Tables 1 and 2. The surface area varied from 330 to 387 m2 g1 . The highly
crystalline ZSM-5 catalysts showed > 343 m2 g1 surface area. The 27 Al solid state NMR results are depicted in Fig. 3. The solid state MAS-NMR analysis was done using Varian unity 400 instru3þ ment. ½AlðH2 OÞ6 Þ used as a standard for 27 Al. With the increase of crystallinity of the ZSM-5 catalyst, the tetrahedral peak intensity increases at 56 ppm ðT1 Þ as shown in Fig. 3. There are two peaks in 27 Al solid state NMR spectra. The peak at 56 ppm corresponds to the tetrahedral Al and the peak of 27 Al at 0.0 ppm ðT2 Þ corresponds to the octahedral aluminum which is not incorporated in the framework. The correlation of ðT1 =T2 Þ to the percent crystallinity has been studied. We could not obtain linear relationship. This may indicate that some of the tetrahedral aluminum is non-framework and that is why the linear relationship between ðAlTetra = AlOct Þ with respect to the percent crystallinity was not observed. The liquid phase reaction of anisole with KBr in the presence of H2 O2 and HZSM-5 was carried out [7]. The results are given in Table 3. The conversion and para selectivity were 99.0% and 98.0%, respectively. The catalysts have shown the desired activity. The acid catalyzed reaction is expected to give linear relationship between the tetrahedral aluminum and acidity and catalytic activity. The other physico-chemical characterizations like Si-solid-state MAS-NMR and catalytic
Table 3 Regioselective oxybromination of anisole: effect of catalysta Entry
1 2 3 4 5 6 7 8 9
Catalyst
Time (h) b
HZSM-5 (Methanol) HZSM-5 (Methanol)b HZSM-5 (Acetone)b HZSM-5 (Ethanol)b HZSM-5 (Isopropanol)b HZSM-5c HY SiO2 –Al2 O3 –
2 2 2 2 2 2 2 2 2
Conversion of anisole (%) 99 99 99 99 99 99 43 44 32
Yield (%) Para
Ortho
98 98 98 98 98 98 43 44 32
– – – – – – – – –
Entry (1): Autoclavation time ¼ 4 h; Entry (2): Autoclavation time ¼ 6 h. a Anisole (6 mmol), KBr (6.6 mmol), 30% H2 O2 (6.6 mmol), acetic acid (4 ml), HZSM-5 (300 mg), r.t. b Solvent used for the preparation of ZSM-5 catalyst. c Commercial catalyst (HZSM-5).
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
117
activity are in progress. The work is being extended to many other molecular sieves.
Dr. B. Jagadeesh for the help in solid state MASNMR.
4. Conclusions
References
The highly crystalline ZSM-5 is synthesized in very short autoclavation time 4–10 h using various solvents under high temperatures (230–260 °C) and high pressures (40–50 atm).
[1] R.J. Argauer, G.R. Landolt, US Patent, 3702886, 1972. [2] H. Robson, Microporous Mater. 22 (1998) 626. [3] R.M. Barrer, Hydrothermal Chemistry of Zeolites, Academic Press, New York, 1982. [4] A. Thangaraj, M.J. Eapen, S. Sivasanker, P. Ratnasamy, Zeolites 12 (1992) 943. [5] P. Kumar, A. Bhaumik, R.K. Ahedi, S. Ganapathy, Nature 381 (1996) 298. [6] S.J. Kulkarni, H. Hattori, K. Tanabe, Appl. Catal. 49 (1989) 27. [7] N. Narender, P. Srinivasu, S.J. Kulkarni, K.V. Raghavan, Synth. Commun. 30 (20) (2000) 3669.
Acknowledgements We are thankful to Council of Scientific & Industrial Research for Senior Research Fellowship to PS. We are thankful to Dr. A.C. Kunwar and
Fast and efficient synthesis of ZSM-5 under high pressure q S.J. Kulkarni *, P. Srinivasu, N. Narender, K.V. Raghavan Catalysis and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500 007, India Received 5 September 2001; received in revised form 16 January 2002; accepted 16 January 2002
Abstract Highly crystalline ZSM-5 catalysts were synthesized in 4–6 h of autoclavation time using various solvents under high pressures ð 40–60 atmÞ and temperatures (230–250 °C) Ó 2002 Published by Elsevier Science B.V.
1. Introduction The US patent of synthesis of ZSM-5 by Argauer and Landolt [1] is the milestone in zeolite catalysis. Initially ZSM-5 was synthesized with 7 days of autoclavation time at 120–180 °C under autogenous pressure. Using nucleated gel [2,3] i.e. seeding method, the autoclavation time was further reduced to two days and the process is commercialized. The autoclavation time was further reduced to 4–12 h by the modified synthesis [4,5]. In case of promoter induced synthesis, there are various problems before it can be commercialized like phase or anion impurity, percent crystallinity, the incorporation of metal ion (e.g. As, P) in the framework tetrahedral position, the yield of the product and control of Si/Al ratio in the product. In this paper we report the synthesis of highly crystalline ZSM-5 at reduced autoclavation time,
4–10 h under high pressure and temperature without using any promoter.
2. Experimental 2.1. The seeding gel for ZSM-5 was synthesized by the following procedure The seeding gel was prepared as follows: 0.69 g (0.01725 mol) of sodium hydroxide was dissolved in 71.028 ml (3.946 mol) of distilled water. 27.7 ml (0.02875 mol) tetrapropylammonium hydroxide was added drop-wise to NaOH solution with stirring. The mixture was stirred for 30 min. Then 27.5 ml (0.1322 mol) of tetraethoxysilane was added drop-wise. The total mixture was stirred at 100 °C for about 16 h. This is used as seeding gel. 2.2. The ZSM-5 was synthesized as follows
q
IICT Communication No. 4790. Corresponding author. Tel.: +91-40-7173874; fax: +91-407173387/757. E-mail address: [email protected] (S.J. Kulkarni). *
Sodium hydroxide 0.88 g (0.22 mol) was dissolved in 25 ml of distilled water. Sodium aluminate 1.05 g (0.0128 mol) and 196 ml (4.841 mol) of methanol as a solvent were added and the mixture
1566-7367/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII: S 1 5 6 6 - 7 3 6 7 ( 0 2 ) 0 0 0 5 1 - 1
95.0 83.0 92.0 74.0 71.0 53.0 – 83.0 361 351 387 364 346 343 333 379 11.6 11.6 11.8 11.3 11.4 11.6 11.2 11.6 Acetone Isopropanol Ethanol Acetonitrile Water 2 3 4 5 6
R ¼ ðSiO2 Þ29:4 : ðAl2 O3 Þ1 : ðTempÞ0:5 : ðH2 OÞ260 .
Methanol 1
R: R: R: R: R:
ðCH3 COCH3 Þ417 ððCH3 Þ2 CHOHÞ400 ðCH3 CH2 OHÞ525 ðCH3 CNÞ586 ðH2 OÞ1701
242 242 242 230 230 233 265 260 R: ðCH3 OHÞ756
Autogenous pressure (atm) Autoclavation temperature (°C) Gel composition Solvent Entry
Fig. 1. X-ray diffraction patterns of (a) ZSM-5 (4 h, methanol), (b) ZSM-5 (6 h, methanol), (c) ZSM-5 (10 h, acetone), (d) ZSM5 (10 h, acetonitrile) (e) ZSM-5 (10 h, ethanol), (f) ZSM-5 (10 h, isopropanol).
Table 1 Synthesis of ZSM-5 with various solvents and under high pressure conditions
Time (h)
Initial pH
The experimental conditions of the synthesis of ZSM-5 are given in Table 1. We have varied the solvents in the synthesis like methanol, ethanol, acetone, acetonitrile, isopropanol and water. The
10.2 10.2 10.1 10.2 10.3 10.3 10.0 10.4
Final pH
3. Results and discussion
4 6 10 10 10 10 10 10
Surface area ðm2 g1 Þ
% Crystallinity
(Si/Al) atomic zeolite
was stirred for 30 min. Tetraethoxysilane 41.9 ml (0.1882 mol) was added drop-wise and stirred for an hour. Finally 15 g of the seeding gel was added and the mixture was stirred for 1 h. The pH of the mixture was 10.2–11.0. The total mixture was put into 600 ml Parr autoclave and stirred at 230–250 °C for 4–10 h. The solid product obtained was filtered, washed with distilled water and dried at 100–110 °C for 6 h.
27.25 – – 17.10 17.63 17.63 16.43 13.85
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
50 49 50 47 48 50 50 47
114
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
115
Fig. 2. Infra-red spectra of (a) ZSM-5 (10 h, methanol), (b) ZSM-5 (10 h, acetone), (c) ZSM-5 (10 h, ethanol), (d) ZSM-5 (10 h, isopropanol).
Fig. 3. 27 Al Solid state MAS-NMR of (a) ZSM-5 (10 h, methanol), (b) ZSM-5 (10 h, isopropanol), (c) ZSM-5 (10 h, acetone), (d) ZSM-5 (10 h, water), (e) ZSM-5 (10 h, ethanol) (f) ZSM-5 (10 h, acetonitrile).
autoclavation pressure was kept near or above critical pressure by increasing the autoclavation temperature above the critical temperature of the
solvent. The autoclavation temperature varied from 230 to 260 °C and the corresponding autogenous pressure from 45 to 50 atm. The initial pH
Table 2 Synthesis of ZSM-5a : effect of temperature Entry
Autoclavation temperature (°C)
Autogenous pressure (atm)
Gel composition
1 2 3 4
242 200 180 150
50 39 34 27
R: R: R: R:
ðCH3 OHÞ756 ðCH3 OHÞ756 ðCH3 OHÞ756 ðCH3 OHÞ756
R ¼ ðSiO2 Þ29:4 : ðAl2 O3 Þ1 : ðTempÞ0:5 : ðH2 OÞ260 . a Methanol used as a solvent.
Time (h)
Initial pH
Final pH
Surface area ðm2 g1 Þ
% Crystallinity
4 4 4 4
10.2 10.1 9.9 9.8
11.6 11.2 11.0 11.1
361 358 342 347
95.0 94.0 95.0 61.0
116
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
was 10–10.4 of gel and the final pH was 11.2–11.8. In the initial pH range of 9–10.5, the homogeneous highly crystalline product is expected with homogeneous aluminum distribution throughout the crystallite [6]. The X-ray diffraction patterns are given in Fig. 1. The XRD patterns were obtained using SIE) radiaMENS D5000, with Cu Ka (k ¼ 1:54 A tion in the range of 0–40 values of 2h. In case of methanol as a solvent the autoclavation time was varied from 4, 6 and 10 h. All the corresponding XRD patterns show high crystallinity. The XRD pattern corresponding to acetonitrile as a solvent was not good and the solid product obtained after 10 h was nearly amorphous. The percent crystallinities are given in Tables 1 and 2. The ZSM-5 catalysts which were synthesized using methanol as a solvent showed P 95% crystallinity. In case of ethanol, acetone or isopropanol as a solvent, the solid products (ZSM-5) obtained were highly crystalline with the impurity of quartz. The attempts are in progress to reduce the impurity by varying the autoclavation temperature. The IR spectra were taken using NICOLET 740 model-FTIR spectrometer, KBr pellets and given in Fig. 2. The IR spectra are characteristic of typical ZSM-5 catalyst. The (Si/Al) atomic ratio was 17 for crystalline catalysts. The surface area are given in Tables 1 and 2. The surface area varied from 330 to 387 m2 g1 . The highly
crystalline ZSM-5 catalysts showed > 343 m2 g1 surface area. The 27 Al solid state NMR results are depicted in Fig. 3. The solid state MAS-NMR analysis was done using Varian unity 400 instru3þ ment. ½AlðH2 OÞ6 Þ used as a standard for 27 Al. With the increase of crystallinity of the ZSM-5 catalyst, the tetrahedral peak intensity increases at 56 ppm ðT1 Þ as shown in Fig. 3. There are two peaks in 27 Al solid state NMR spectra. The peak at 56 ppm corresponds to the tetrahedral Al and the peak of 27 Al at 0.0 ppm ðT2 Þ corresponds to the octahedral aluminum which is not incorporated in the framework. The correlation of ðT1 =T2 Þ to the percent crystallinity has been studied. We could not obtain linear relationship. This may indicate that some of the tetrahedral aluminum is non-framework and that is why the linear relationship between ðAlTetra = AlOct Þ with respect to the percent crystallinity was not observed. The liquid phase reaction of anisole with KBr in the presence of H2 O2 and HZSM-5 was carried out [7]. The results are given in Table 3. The conversion and para selectivity were 99.0% and 98.0%, respectively. The catalysts have shown the desired activity. The acid catalyzed reaction is expected to give linear relationship between the tetrahedral aluminum and acidity and catalytic activity. The other physico-chemical characterizations like Si-solid-state MAS-NMR and catalytic
Table 3 Regioselective oxybromination of anisole: effect of catalysta Entry
1 2 3 4 5 6 7 8 9
Catalyst
Time (h) b
HZSM-5 (Methanol) HZSM-5 (Methanol)b HZSM-5 (Acetone)b HZSM-5 (Ethanol)b HZSM-5 (Isopropanol)b HZSM-5c HY SiO2 –Al2 O3 –
2 2 2 2 2 2 2 2 2
Conversion of anisole (%) 99 99 99 99 99 99 43 44 32
Yield (%) Para
Ortho
98 98 98 98 98 98 43 44 32
– – – – – – – – –
Entry (1): Autoclavation time ¼ 4 h; Entry (2): Autoclavation time ¼ 6 h. a Anisole (6 mmol), KBr (6.6 mmol), 30% H2 O2 (6.6 mmol), acetic acid (4 ml), HZSM-5 (300 mg), r.t. b Solvent used for the preparation of ZSM-5 catalyst. c Commercial catalyst (HZSM-5).
S.J. Kulkarni et al. / Catalysis Communications 3 (2002) 113–117
117
activity are in progress. The work is being extended to many other molecular sieves.
Dr. B. Jagadeesh for the help in solid state MASNMR.
4. Conclusions
References
The highly crystalline ZSM-5 is synthesized in very short autoclavation time 4–10 h using various solvents under high temperatures (230–260 °C) and high pressures (40–50 atm).
[1] R.J. Argauer, G.R. Landolt, US Patent, 3702886, 1972. [2] H. Robson, Microporous Mater. 22 (1998) 626. [3] R.M. Barrer, Hydrothermal Chemistry of Zeolites, Academic Press, New York, 1982. [4] A. Thangaraj, M.J. Eapen, S. Sivasanker, P. Ratnasamy, Zeolites 12 (1992) 943. [5] P. Kumar, A. Bhaumik, R.K. Ahedi, S. Ganapathy, Nature 381 (1996) 298. [6] S.J. Kulkarni, H. Hattori, K. Tanabe, Appl. Catal. 49 (1989) 27. [7] N. Narender, P. Srinivasu, S.J. Kulkarni, K.V. Raghavan, Synth. Commun. 30 (20) (2000) 3669.
Acknowledgements We are thankful to Council of Scientific & Industrial Research for Senior Research Fellowship to PS. We are thankful to Dr. A.C. Kunwar and