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Vinyl Polymerization of Norbornene over Supported Nickel Catalyst
Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.
209
35
Vinyl Polymerization of Norbornene over Supported Nickel Catalyst Junxian Hou, Wenjuan Zhang, Suyun Jie and Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
Abstract The nickel(ll) complex was immobilized onto spherical MgCl2, and performed norbornene polymerization in the existence of MAO. Spherical polymer particle morphology was observed without reactor fouling. 1. INTRODUCTION In recent years nickel-based complexes are becoming one type of important catalysts for vinyl polymerization of norbornene due to their high catalytic activities [1]. We have synthesized various nickel complexes bearing ligands of [N,O] [2] and [P,N] [3] for norbornene polymerization, however, those homogeneous catalysis resulted in a serious fouling of the reactor. The silica, silica-alumina derivatives, MgCl2 [4] and polymeric materials [S] are commonly used as supports. Therefore the immobilization and activation of the nickel complex 1 [2b] benefits the application in norbornene polymerization. 2. EXPERIMENTAL Bis-[JV-(diphenylmethyl)-salicylideneiminato]nickel(Il) (1) [2] and spherical MgCl2"nEtOH [4a, 6] were prepared according to the literature. Morphologies of the PNB particles, the catalysts were examined on a HITACHI S-4300 scan electron microscope. Elemental analysis was performed by spectrophotometry Shimadzu UV-2401PC and titration technique. Nitrogen adsorption-desorption isotherms were measured at 77 K using an ASAP2010 volumetric adsorption
210
J.Houetal
apparatus. Molecular weights were determined by Waters Alliance GPCV 2000 system at 135 °C in 1,2,4-trichlorobenzene. Viscosity measurements were carried out in chlorobenzene at 25 °C using an LJbbelohde viscometer. Typical preparation of MgCl2 supported nickel catalyst 6: To 40 ml hexane solution containing 4.64 g spherical MgCl2-2.97C2HsOH (20.0 mmol) in a 500 ml four-necked flask, 42.9 ml toluene solution of 1.4 M MAO was added over a period of 30 min, and reacted at -30 °C for 4 h. The slurry was filtered under N2 and the solid was washed twice by »-hexane (30 ml x2), dried under N2. The resulting powder was placed in the flask containing 30 ml toluene and the slurry was stirred at 25 °C, 50 ml toluene containing nickel complex 1 (0.22 mmol) was added to the slurry and stirred for 4 h. The final product was washed with toluene, until the liquid layer above became colorless. The solid catalyst (SNC1) was dried in vacuo until free flowing conditions were reached. Polymerization of norbornene: In a 100 mL Schlenk tube, the Ni catalyst (5 umol Ni), 14.08 mL toluene and 3.78 mL solution of norbomene in toluene (6.61 M) were introduced. The polymerization was initiated by addition of a 7.14 mL toluene solution of 1.4 M MAO via syringe. After 60 min, the reaction was terminated by pouring into 200 mL acidic MeOH (MeOH:HClBOTlc= 95:5). 3. RESULTS AND DISCUSSION Effects of supporting conditions: Elemental analysis, surface areas of the supported catalysts are shown in Table 1. Treatment of spherical MgCl2*nEtOH adduct produces dealcoholization without structure collapse [6]. The results indicate that Al loading on the support greatly decreased upon decreasing of the ethanol content in the MgCl2/ethanol adducts. The Ni loading increased in the order of SNC-1 < SNC-2 < SNC-3 < SNC-4. The BET surface areas and pore volume increased upon decreasing the ethanol content in its MgCl2 adduct. There was no significant change in polymer molecular weight relying on various ratio of EtOH to MgCl2 in the range of 1.50-1.98x10* g/mol. The catalytic activities are in the range of 238-281 kg PNB/mol Nrh. SNC-2 was chosen for study in detail at different conditions for its good morphology. Effects of polymerization conditions: Lower activity was observed in hexane while higher activity was obtained in toluene. However, higher molecular weights of the resulted PNBs were obtained in hexane as solvent. Increase of monomer concentration, the M/Ni ratio (M: norbomene), causes rapid increase of the activities combined with a drastic increase of molecular weight. Morphology of the PNB particles changed gigantically with monomer concentration. At an M/Ni ratio of 10000:1, polymer particle started to agglomerate along with reactor fouling, and therefore morphological control was gradually lost.
35. Vinyl Polymerization
ofNorbornene
over Supported Ni Catalyst
211
Table 1 Element analysis and BET analysis of supported catalysts Catalyst
BET ^ ^
Pore vol. ( m L / 8)
Average pore Diameter (A)
7.65
1.5
0.018
477
16.22
5.12
5.4
0.022
162
0.24
16.87
3.60
12.3
0.047
152
0.26
21.52
3.49
18.7
0.093
198
Starting
Ni
Mg
Al
material
wt.%
wt.%
wt.%
SNC-1
MgCl2-2.97Et0H
0.18
10.32
SNC-2
MgCl2-1.72EtOH
0.23
SNC-3
MgCl2'1.30EtOH
SNC-4
MgCl2-0.38EtOH
The treating spherical MgCl^ support with MAO was carried out at -30°C. Table 2. Polymerization of norbornene with supported l a Entry
Catalyst
M/Ni
Yield
Activity11
E
SNC-1
5000
59.7
MJMn
(dL/g)
g/mol)
281
1.06
16.1
4.91
% 1
M w (xl0 s
2C
SNC-1
5000
50.6
238
1.11
18.7
3.85
3
SNC-2
5000
56.9
268
1.10
19.8
5.70
4
SNC-3
5000
53.7
253
0.94
15.2
4.97
5
SNC-4
5000
51.6
243
0.96
15.0
5.76
6
SNC-2
2500
32.2
76
0.77
9.01
4.19
7
Ni(II)
2500
58.2
136
0.65
3.54
3.17
d
8
SNC-2
7500
83.3
5S8
1.39
n.d
n.d.
9
SNC-2
10000
65.9
621
1.48
n.d.
n.d.
Condition: 5 jimol Ni; 25°C; toluene; 60 min; total volume, 25 mL; M / Ni = 5000 ; MAO, Al/Ni = 2000." kg PNB/mol Nrh. c Hexane as solvent. d Not determined.
The activity of the heterogeneous catalyst is ca. 50-70% of its homogeneous catalyst under the same conditions (entry No 6, 7) in Table 2, which is a wellknown phenomenon [7-10] in olefm polymerization. However, comparing entries 6 and 7, the molar mass of the polynorbornene obtained with SNC-2 was around two times higher than that obtained with the homogeneous catalyst 1. The broadening of the molecular weight distributions was evident with the supported catalyst systems. Often the PDI values in the literature are higher for supported catalysts compared to homogeneous system [4b, 7]. Microscopy studies: Fig. la showed that spherical MgCl2-2.97EtOH had a smooth and less porous surface. The supported catalyst (Fig. lb) appeared a rough and porous surface. Fig. lc showed its PNB particle with 15-20 times larger than that of the catalyst SNC-2 (typical 30 um).
212
J. Hou et al.
Fig. 1. SEM micrographs, (a) spherical MgClz-2.97Et0H (600x), (b) SNC-6 (600x), (c) PNB particles (entry 11, 40x).
4. CONCLUSIONS Bis-[N-(diphenylmethyl)-salicylideneiminato]nickel(IT) (1) was supported on spherical MgCl2. The supported catalysts performed well for norbornene polymerization with fine morphology and high activity. The polynorbornenes produced with supported catalyst have higher molecular weight and broader molecular weight distribution than those of its homogeneous ones. Acknowledgements The project supported by NSFC 20473099. This work was partly completed in Polymer Chemistry Laboratory, Chinese Academy of Sciences and China Petro-Chemieal Corporation. References [1]
B. Berchtold, V. Lozan, P-G. Lassahn, C. Janiak, J. Polym. Sci. Polym. Chem. 40 (2002) 3604. [2] H.Yang, W.-H. Sun, F. Chang, Y. Li. Appl. Cat. A. 252 (2003) 261. [3] H. Yang, Z. Li, W.-H. Sun. J. Mol. Catal. A: Chem. 206 (2003) 23. [4] a) R. Huang, D. Liu, S. Wang, B. Mao, Macromol. Chem. Phys. 205 (2004) 966; b) H. S. Cho, W. Y. Lee, J. Mol. Catal. A. 191 (2003) 155. [5] T. R. Boussie, V. Murphy, K. A. Hall, C. Coutard, C. Dales, M. Petro, E. Carlson, H. W. Turner, T. S. Powers, Tetrahedron 55 (1999) 11699. [6] P. Sozzani, S. Bracco, A. Comotti, R. Simonutti, I. Camurati, J. Am. Chem. Soc. 125(2003)12881. [7] F. AlObaidi, Z. Ye, S. Zhu, Macromol. Chem. Phys. 204 (2003) 1653. [8] S. Collins, W. M. Kelly, D. A. Holden, Macromolecules 25 (1992) 1780. [9] M. O. Kristen, Top. Catal. 7 (1999) 89. [10] S. I. Woo, Y. S. Ko, T. K. Han, Macromol. Chem. Phys. 16 (1995) 489.
209
35
Vinyl Polymerization of Norbornene over Supported Nickel Catalyst Junxian Hou, Wenjuan Zhang, Suyun Jie and Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
Abstract The nickel(ll) complex was immobilized onto spherical MgCl2, and performed norbornene polymerization in the existence of MAO. Spherical polymer particle morphology was observed without reactor fouling. 1. INTRODUCTION In recent years nickel-based complexes are becoming one type of important catalysts for vinyl polymerization of norbornene due to their high catalytic activities [1]. We have synthesized various nickel complexes bearing ligands of [N,O] [2] and [P,N] [3] for norbornene polymerization, however, those homogeneous catalysis resulted in a serious fouling of the reactor. The silica, silica-alumina derivatives, MgCl2 [4] and polymeric materials [S] are commonly used as supports. Therefore the immobilization and activation of the nickel complex 1 [2b] benefits the application in norbornene polymerization. 2. EXPERIMENTAL Bis-[JV-(diphenylmethyl)-salicylideneiminato]nickel(Il) (1) [2] and spherical MgCl2"nEtOH [4a, 6] were prepared according to the literature. Morphologies of the PNB particles, the catalysts were examined on a HITACHI S-4300 scan electron microscope. Elemental analysis was performed by spectrophotometry Shimadzu UV-2401PC and titration technique. Nitrogen adsorption-desorption isotherms were measured at 77 K using an ASAP2010 volumetric adsorption
210
J.Houetal
apparatus. Molecular weights were determined by Waters Alliance GPCV 2000 system at 135 °C in 1,2,4-trichlorobenzene. Viscosity measurements were carried out in chlorobenzene at 25 °C using an LJbbelohde viscometer. Typical preparation of MgCl2 supported nickel catalyst 6: To 40 ml hexane solution containing 4.64 g spherical MgCl2-2.97C2HsOH (20.0 mmol) in a 500 ml four-necked flask, 42.9 ml toluene solution of 1.4 M MAO was added over a period of 30 min, and reacted at -30 °C for 4 h. The slurry was filtered under N2 and the solid was washed twice by »-hexane (30 ml x2), dried under N2. The resulting powder was placed in the flask containing 30 ml toluene and the slurry was stirred at 25 °C, 50 ml toluene containing nickel complex 1 (0.22 mmol) was added to the slurry and stirred for 4 h. The final product was washed with toluene, until the liquid layer above became colorless. The solid catalyst (SNC1) was dried in vacuo until free flowing conditions were reached. Polymerization of norbornene: In a 100 mL Schlenk tube, the Ni catalyst (5 umol Ni), 14.08 mL toluene and 3.78 mL solution of norbomene in toluene (6.61 M) were introduced. The polymerization was initiated by addition of a 7.14 mL toluene solution of 1.4 M MAO via syringe. After 60 min, the reaction was terminated by pouring into 200 mL acidic MeOH (MeOH:HClBOTlc= 95:5). 3. RESULTS AND DISCUSSION Effects of supporting conditions: Elemental analysis, surface areas of the supported catalysts are shown in Table 1. Treatment of spherical MgCl2*nEtOH adduct produces dealcoholization without structure collapse [6]. The results indicate that Al loading on the support greatly decreased upon decreasing of the ethanol content in the MgCl2/ethanol adducts. The Ni loading increased in the order of SNC-1 < SNC-2 < SNC-3 < SNC-4. The BET surface areas and pore volume increased upon decreasing the ethanol content in its MgCl2 adduct. There was no significant change in polymer molecular weight relying on various ratio of EtOH to MgCl2 in the range of 1.50-1.98x10* g/mol. The catalytic activities are in the range of 238-281 kg PNB/mol Nrh. SNC-2 was chosen for study in detail at different conditions for its good morphology. Effects of polymerization conditions: Lower activity was observed in hexane while higher activity was obtained in toluene. However, higher molecular weights of the resulted PNBs were obtained in hexane as solvent. Increase of monomer concentration, the M/Ni ratio (M: norbomene), causes rapid increase of the activities combined with a drastic increase of molecular weight. Morphology of the PNB particles changed gigantically with monomer concentration. At an M/Ni ratio of 10000:1, polymer particle started to agglomerate along with reactor fouling, and therefore morphological control was gradually lost.
35. Vinyl Polymerization
ofNorbornene
over Supported Ni Catalyst
211
Table 1 Element analysis and BET analysis of supported catalysts Catalyst
BET ^ ^
Pore vol. ( m L / 8)
Average pore Diameter (A)
7.65
1.5
0.018
477
16.22
5.12
5.4
0.022
162
0.24
16.87
3.60
12.3
0.047
152
0.26
21.52
3.49
18.7
0.093
198
Starting
Ni
Mg
Al
material
wt.%
wt.%
wt.%
SNC-1
MgCl2-2.97Et0H
0.18
10.32
SNC-2
MgCl2-1.72EtOH
0.23
SNC-3
MgCl2'1.30EtOH
SNC-4
MgCl2-0.38EtOH
The treating spherical MgCl^ support with MAO was carried out at -30°C. Table 2. Polymerization of norbornene with supported l a Entry
Catalyst
M/Ni
Yield
Activity11
E
SNC-1
5000
59.7
MJMn
(dL/g)
g/mol)
281
1.06
16.1
4.91
% 1
M w (xl0 s
2C
SNC-1
5000
50.6
238
1.11
18.7
3.85
3
SNC-2
5000
56.9
268
1.10
19.8
5.70
4
SNC-3
5000
53.7
253
0.94
15.2
4.97
5
SNC-4
5000
51.6
243
0.96
15.0
5.76
6
SNC-2
2500
32.2
76
0.77
9.01
4.19
7
Ni(II)
2500
58.2
136
0.65
3.54
3.17
d
8
SNC-2
7500
83.3
5S8
1.39
n.d
n.d.
9
SNC-2
10000
65.9
621
1.48
n.d.
n.d.
Condition: 5 jimol Ni; 25°C; toluene; 60 min; total volume, 25 mL; M / Ni = 5000 ; MAO, Al/Ni = 2000." kg PNB/mol Nrh. c Hexane as solvent. d Not determined.
The activity of the heterogeneous catalyst is ca. 50-70% of its homogeneous catalyst under the same conditions (entry No 6, 7) in Table 2, which is a wellknown phenomenon [7-10] in olefm polymerization. However, comparing entries 6 and 7, the molar mass of the polynorbornene obtained with SNC-2 was around two times higher than that obtained with the homogeneous catalyst 1. The broadening of the molecular weight distributions was evident with the supported catalyst systems. Often the PDI values in the literature are higher for supported catalysts compared to homogeneous system [4b, 7]. Microscopy studies: Fig. la showed that spherical MgCl2-2.97EtOH had a smooth and less porous surface. The supported catalyst (Fig. lb) appeared a rough and porous surface. Fig. lc showed its PNB particle with 15-20 times larger than that of the catalyst SNC-2 (typical 30 um).
212
J. Hou et al.
Fig. 1. SEM micrographs, (a) spherical MgClz-2.97Et0H (600x), (b) SNC-6 (600x), (c) PNB particles (entry 11, 40x).
4. CONCLUSIONS Bis-[N-(diphenylmethyl)-salicylideneiminato]nickel(IT) (1) was supported on spherical MgCl2. The supported catalysts performed well for norbornene polymerization with fine morphology and high activity. The polynorbornenes produced with supported catalyst have higher molecular weight and broader molecular weight distribution than those of its homogeneous ones. Acknowledgements The project supported by NSFC 20473099. This work was partly completed in Polymer Chemistry Laboratory, Chinese Academy of Sciences and China Petro-Chemieal Corporation. References [1]
B. Berchtold, V. Lozan, P-G. Lassahn, C. Janiak, J. Polym. Sci. Polym. Chem. 40 (2002) 3604. [2] H.Yang, W.-H. Sun, F. Chang, Y. Li. Appl. Cat. A. 252 (2003) 261. [3] H. Yang, Z. Li, W.-H. Sun. J. Mol. Catal. A: Chem. 206 (2003) 23. [4] a) R. Huang, D. Liu, S. Wang, B. Mao, Macromol. Chem. Phys. 205 (2004) 966; b) H. S. Cho, W. Y. Lee, J. Mol. Catal. A. 191 (2003) 155. [5] T. R. Boussie, V. Murphy, K. A. Hall, C. Coutard, C. Dales, M. Petro, E. Carlson, H. W. Turner, T. S. Powers, Tetrahedron 55 (1999) 11699. [6] P. Sozzani, S. Bracco, A. Comotti, R. Simonutti, I. Camurati, J. Am. Chem. Soc. 125(2003)12881. [7] F. AlObaidi, Z. Ye, S. Zhu, Macromol. Chem. Phys. 204 (2003) 1653. [8] S. Collins, W. M. Kelly, D. A. Holden, Macromolecules 25 (1992) 1780. [9] M. O. Kristen, Top. Catal. 7 (1999) 89. [10] S. I. Woo, Y. S. Ko, T. K. Han, Macromol. Chem. Phys. 16 (1995) 489.